Telephone-exchange system



FIG. I

Aug. 10 1926., U 1,595,083

E. S. GIBSON TELEPHONE EXCHANGE SYSTEM ed July 16, 192.4 5 Sheets-Sheet 1 Q 9. LL-

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E. S. GIBSON 4 TELEPHONE EXCHANGE SYSTEM Filed July 16, 1924 5 Sheets-Sheet 3 //7 venfar: [ar/ 5.- fi/Qsgp b Am E. S. GIBSON TELEPHONE EXCHANGE SYSTEM Filed July 16, 1924 5 Sheets-Sheet 4 Aug- 10,1926. I 1,595,083

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' E. S. GlBSON TELEPHONE EXCHANGE SYSTEM /n venfar; far/ 5. Gibson Patented Aug. 10, 1926.

UNITED STATES EARL S. GIBSON, OF RIDGEVIOOD, NEW JERSEY, .ASSIGNOR TO WESTERN ELECTRIC COM PATENT OFFICE.

PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OENEW YORK. 7

TELEPHONE-EXCHANGE SYSTELI.

Application filed July 16, 1924. Serial No. 726,241.

This invention relates to telephone exchange systems, and more particularly to systems employing automatic switching apparatus for establishing connections.

.For systems involving equipment for the completion of toll and long distanceconnections, it is desirable to permit the completing operator to set up connection to a called line although such line may be busy at the 10 time. By thus interposing, the operator may apprise the called party that a toll call is waiting his attention, giving him the option of continuing his present conversation or of discontinuing the same and receiving the toll call. If he decides to disregard the call, the operator must then release the switches which have built up the connection to his line. Inasmuch as the sleeve conductor of the operators connection has been extended to the sleeve conductor of the called line, which is busy, this busy condition would ordinarily be transmitted to the sleeve conductor of said connection, thereby preventing the operator from releasing the switches she had set.

Accordingly, it is the object of this invention to enable the release of connections which have been set up to busy lines.

A feature of the invention relates to means for extending a connection over a trunk to a.line, the release of the trunk being normally under the control of said line, together with means for rendering the release control of such trunk independent of the line to enable the release of the trunk after a conversational connection has been extended to the line when it is busy.

Another feature relates to an arrangement including coordinate connector switch having special link circuit whereby the release of a connection over an incoming trunk to a called line may either be placed under the control of the called line or may be effected immediately by an operator independent of the continued busy condition of said line.

Other advantages of this invention will appear more specifically from the following detailed description and also from the appended claims.

Referring to the drawing, Figs. 1 to 5, inclusive, when taken in the order illustrated in Fig.- 6, disclose a suliicient amount of a telephone exchange system employing the features of this invention to enable an understanding thereof.

Fig. 1 at the top illustrates schematically a local connection extended through a line switch and a district elector switch. At tl e bottom of this figure there is illustrated an incoming trunk from a distant oiiice, together with an operators position and her position equipment. The figure also shows schematically a sender selector switch and one of a number of registersenders.

illustrates a portion of two different incoming selector switches.

Fig. 3 illustrates a portion of a final or connector switch having access to called subscribers lines.

Fig. t shows a part of one of a number of switch controlling markers and also a connecting device for associating these markers with the senders.

Fig. 5 illustrates schematically frame and trunk connectors for associating the markers Jltll the incoming and final switches.

The system disclosed herein is arranged to handle both local calls and calls incoming from distant otlices. The local lines 100 terminate in line switches 101 which have access to trunks as 102 leading to district selector switches as 103. The district selector switches 103 have access to trunks such as 115, which terminate in vertical rows of contacts 213 and 214 on incoming selector switches as 200. The incoming selector switches 200, only one of which is shown herein, have access to groups of trunks extending to final connector switches 300. For instance, one group of trunks may appear in the vertical row of contacts 215, while another group of trunks appear in the vertical row of contacts 216, etc.

The connector switches 800 are dividel into a number of groups, each group having access to a different portion of the total subscribers lines. The group of trunks appearing in the vertical row 215 comprising the trunk 217, 218 etc, extend and appear in connector switches of a particular group. The group of trunks appearing in the vertical row 216 of the incoming switch 200 comprising the trunks 219 and 220, extend and appear in a different group of connector switches one of which, switch 800, is shown. For instance, the trunk 220 which is shown in full herein appears in the vertical row of contacts 301 in the connector switch 300 having access to a hori-.

Zontal link in each of the units sections 310, 311 of the switch. Likewise, other groups of trunks outgoing from the incoming switches 200 appear in still other groups of connector switches. Each of the trunks of the several groups are multipled to appear in all of the incoming switches comprising a particular group.

In addition to the equipment provided for local calls, the oliice is also provided with operators positions as shown in Fig. 1. The trunks, such as trunk 106, incoming from distant oiiices may serve to extend toll or long distance connections or for other similar purposes, and these trunks appear in the vertical rows of contacts of a special group of incoming selector switches one of which, switch 201, is illustrated. The particular trunk 106, which is only shown par tially, will be seen to appear in the vertical row of contacts 202 of the switch 201. Another trunk of similar nature and also under the control of the operator appears in row 203. At each operators position there are provided a keyboard 105, an assignment key 112 and a release key 118 individual to each of the trunks over which such operator has control.

The special incoming selector switches 201 have access to groups of operators trunks extending to the several different groups of connector switches. tical row of contacts 205 may include several of these operators trunks, all of which lead to connector switches 300 of the same connector group. at will. be noted that the trunk 220 appearing in the row 205 is also the same trunk which is multipled to appear in the row 210 of the regular incoming selector switches 200. This trunk will be the last trunk in the group with respect to the incoming selector switches 200. The next operators trunk 222 appearing in the row 205 of switch 201 will be the last trunk in another group of trunks outgoing from the incoming switches 200 appearing in the same group of connector switches 300. Similarly, the same is true with respect to trunks 223 and 227. Thus, trunks 220, 222, 223 and 227 are each respectively the last trunk in four different groups of trunks outgoing from the incoming selector switches 200 to the same group of connector switches including switch 300: and these four ditlerent operators trunks are all combined in the same vertical row of contacts 205 in the special incoming switches 201. In a similar manner, the tour operators trunks appearing in the vertical row 204 of switches 201 are the last trunks in tour corre ponding groups outgoing from the incoming switches 200 and appearing in a second group of connector switches 300. The same may be true for as many groups For example, the verof such markers being this purpose sender of connector switches 300 as there are pro vided.

Thus it will be seen that these special operators trunks 220, etc., serve both for local mechanical connections and are also employed for interoiiice connections where an operator is involved.

The operators trunks of a particular group are arranged to appear before a corresponding horizontal link on each of the several connector switches 300 of the connector group. Each trunk, however, ap pears in a different vertical row otcontacts of the connector switches 300. For example, the trunk 220 appears before the horizontal links 313, 31 i, etc., in the vertical row 301 of the connector switch 300 and similarly before corresponding links in other connector switches. The second trunk 222 appears before the links 313, 314L,Vetc., in the vrrtical row 302 of the connector 300. .1 he same is true with respect to the other trunks of the operators trunk group.

Both the local trunks 102 and the incoming trunks 106 may be associated with idle register senders by means of sender selector switches. In practice there may be two types of senders 107 one to be used for local connections and the other to, be used for incoming calls. trunks 102 may be associated with one kind of sender through one sender selector switch 104lwhercas the incoming trunks 100 may be associated with the other kind of sender through another sender selector 104. For convenience in the drawing, however, both local and incoming trunks have been shown as appearing in the single sender selector frame 104 and no attempt has beenmade to disclose the details of the different types 01" senders.

Each of the several register sender s, such as the sender 107, may be associated with any one of number of markers, part of one shown in l. connector device 400 made up of a number of niulti-contact relavs is provided for connecting any one of tie sc tiers to the first idle marker. The marker receives the record registered in thesender and thereupon determines the selective operation of the incoming and final switches to complete the connection to the wanted line.

After the record has been received in the marker, such marker is associated with an incoming switch frame by means of a frame connector 500. The group oi testing relays 401 in the marker are thereby connected to the test conductors of the horizontal links of the incoming switch. In case the con nection being extended is one involving a local line and thereby involving the incoming switch 200, the marker is further associated with the trunks outgoing from the Accordingly the local incomim switch to the connector switch by means or a trunk connector 501.

Moreover, the marker is associated through a connecting device with the proper connector switch 300 in the particular group, having access to the called subscribers line. By reason oi this association, the testing relays 40.1 are connected to the horizon tal links oi' the proper units sections 310 or 311, etc, in the connector switch. Thus a test is made to determine. an idle link in the lRCOllllGQ, switch corresponding to an idle trunk leading to a connector switch in which a corresponding link is idle at the time. Having determined the idle link and trunk, the incoming and connectorswitches are operated and the connection is extended through to the called line.

In the event that the operator is extending a connection through one of the incoming switches 201 involving only operators trunks, the marker is associated with these trunks by means of one of a number of relays 503, 504, etc.

For an ordinary trunk group outgoing from one of the regular incoming switches 1200, there will be a comparatively large number 01' trunks requiring a corresponding number of sets of test relays 401. The last four of these sets of test relays only are illustrated in the drawing, comprising the relays 408 to 419, inclusive. In the case, however, of calls extended through the special incoming switches 201, the-operators trunk groups provided for this purpose comprise a comparatively small number, as for example, four trunks. Accordingly, only four sets of test relays 401 in the marker are required. Therefore, the relays 503 and 504 above mentioned are provided for connecting the sleeve conductors of these small groups 015' operators trunks with the particular our test relays shown in full in the drawing. ll: the called line occurs in the particu lar group of connector switches illustrated, then the connecting device 502 will have been operated to associate the marker with the proper switch in this group of connector switches, and accordingly the relay 503 is operated to identify the group of trunks apper ng in the vertical row 205 of the incomin switch 201. This particuliar group of ti nlrs the one, of course, which leads to the connector switches of the group having access to the called line. Should the called line occur in another connector group, then a relay such as the relay 504 would be operated to associate the marker test relays vith the group of trunks appearing in the row 20-l which lead to such other connector gup. The relay 504 is operated by reason of the fact that some other connecting device similar to the device 502 has been brought into use for associating the marker with the corresponding connector group.

1 l 111211 A al S, tintl The selective switches illustrated in this drawing may be of the type. shown and dcscrihed in the application of C. L. Goodrum and J. N. Reynolds, Serial No. 486,442, filed July 21, 1921, Patent No. 1,5l5,7 35, granted :lOVCYIilOQi 18, 1924, and also further described in the application of S. B. iVilliams, Serial No. 596,179, filed Qctober 23, 1922, Patent No. 1,517,331, granted December 2, 1924.

The senders 1 7. connecting devices 400,

the frame and trunk connecting devices sn iwn in Fig. have been illus trated in abbreviated "form, inasmuch as a cemplet di closure of these mechanisms is not essential to a complete understanding or the present inven n. For a more complete description of tee operation of thesedevices, reference may be had to the applicr lion of S. B. ll illiains, Serial No. 707,795, "filed April 21, 1924.

[femurs/imam of an. intcroflice connection.

First it will be assumed that a connection is to be established over one of the interoiiice trunks through incoming and connector switches to the called subscribers line 307. in any well known manner the operators attention is called to the fact that a connection needs her assistance. She thereupon assigns the trunk 10 for this purpose and operates an individual assignment key 112, which results in the association of the keyboard 105 with an idle register sender 107 through the agency of the sender selector switch 104. The operator at the distant ofiice upon receiving the assignment of trunk 106, extends the connection over that trunk in the usual manner and also commun icates to the operator in the oi'lice shown the designation of the called subscribers line 307. The operator now proceeds to set up the number on her keyboard, whereafter the record thus recorded is transferred through the sender selector 104 to the regi ters of the sender 107 (not shown). The manner in which these operations take place is described in the application of E. S. Gibson, Serial No. 656,742, filed August 10, 1923, Patent No. 1,559,244, granted October 27, 1925.

After the sender has received the record, the sender connector device 400 is operated, associating the sender 107 with the marker shown in the drawing. Thereupon the rec ord is transferred from the registers of the sender to corresponding registers in the marker. lere the record is translated and the proper connecting'device 502 is selected for associating the marker with the proper group of connector switches 300. it suming the connecting device 502 shown is the one to be used, then the relay 505 individual to the particular marker shown is operated. Moreover, the relay 506 which represents an o the units section 310 in the particular connector switch 300, is also operated. One of the vertical magnets 306 which controls the row of contacts 304 in which appearsthe called line 307, has been operated in accordance with the translated record received in the marker.

After the marker has been associated with the sender, the proper frame connector 500 is selected and operated for associating such marker with the horizontal links of the incoming selector trai'i'ie 201. The operation of this device consists in energizing the relay 507, which causes the operation of multicontact relay 510, The circuit for relay 507 extends from battery, through the wind ing said relay, conductor 503, front contact of relay 406, back contact ot relay 405, to ground at the contact. of holding relay 402, this latter relay having operated when the m. :ker was taken for use. It will be noted that the relay 406 is operated at this time in a circuit from battery through its winding, through the connector device 400,

conductor 420Qback contact o1" rela 111 conductor 421, device 400, conductor 422, to ground at the outer left contact of relay 402.

at the time the connection is extended to the incoming switch 201, the vertical magnet 206 controlling the row of contacts 202 is operated to prepare all of the contacts in this row. The operation of magnet 206 msults in the operation of the multi-contact relay 500, which is individual to the particular incoming frame 201. With rela s and 510 operated, the test relays ot the marker 401 are connected to the corresponding test conductors of the links in switch 201.

Since the called line 307 occurs in the group of connector switches 800 to which lead the group of trunks appearing in the vertical row 205 of the switch 201, the corresponding vertical operating magnet 207 is energized to prepare the contacts of this row. The apparatus is now in readiness for making a test of the horizontal links in the switch 201 and the operators trunks outgoing from the vertical row 205, and also for making a test of a particular horizontal link, such as link 313, having access to the called line 307. For instance, it' the line 307 appears in a connector switch 300 to which each of the tour operators trunks re spectively lead, then a test is made oi. the particular link 313 shown.

Before the marker can make a test of the links and trunks, however, it is necessary to associate the marker with the trunks of the selected group of operators trunks. At the time the register sender 107 is associated with the marker and when the frame connector 500 has been operated, the relay 109 of the sender is operated to indicate that the connection being extended is one involving an operator. The circuit for this relay may be traced from battery, through its winding and normal contact, through the connecting device 400, conductor 425, through contacts ot relay 510, contacts of relay 509, thence through contacts of relay 510, conductor 511, to ground at the contact of holding relay 402. Relay 109 operates and locks to ground 7 atthe contact of the holding relay 108 which has previously been operated. hen relay 100 operated, a circuit was closed or oper ating the relay 404 in the marker, traceable from battery, through the winding of relay 40-4, through contacts or the device 400, left contacts of relay 109, conductor 421, and thence through connecting device 400 to ground at the contact of relay 402.

Relay 404 operates the relay 503 which serves to connect the marker test relays to the sleeve conductors of the operators trunks of the selectec group. The circuit for this purpose may be traced from battery, through the winding of relay 503, contact oi relay 505, to ground at the contact ofrelay 404.

The testing circuits for the links and trunks will now be traced. The circuit for testing the horizontal link 226 may be traced from battery, through the left winding of test relay 408, contact.- of relay 407, t ience through the connecting device 500 to the sleeve conductor of link 226. Similarly, test circuits may be traced from battery, through the left windings of relays 409, 410 and 411 for the horizontal links 225, 224 and The test circuit for testing the operators trunk 220 may be traced from battery through the right winding of relay 411, contact of relay 407, inner right contact of relay 419, conductor 423, contact of relay 503, to the sleeve conductor of the operators trunk 220. Likewise, test circuits for the operators trunks 227, 223 and 222 may be traced through the right windings of'relays 408, 409 and 410, respectively. Any of these test relays will operate provided the circuit is closed through eitherof its windings or if both windings are energized.

Lastly, a test is made to ascertain the condition of the horizontal link 313 of the connector switch before which each of the tour operators trunks appears. The circuit for this purpose may be followed from battery, through the winding of relay 415, conductor 426, connector device 502, conductor 512, to the test conductor 316on the link 313. If the link is busy, relay 415 operates.

It will be assumed that one or more of the horizontal links 226, 225 and 224 and the corresponding trunks 227, 223 and 222 are busy, so that the corresponding test relays 408, 409 and 410 are energized. It will also be assumed that the link 233, the trunk 220 and the link 313 are all idle. Accordingly, the

relay 411 and the relay 415 remain deener-- gized.

As soon'as the test has taken place, a circuit is completed from ground, through the contact of relay 402, thence over conductor 427, inner right front contact of relay 404-, back contact of relay 415, left front contacts of relays 408, 409 and 410, left bacr contact of relay 411, winding of relay 419, to battery. Relay 419-operates and causes the energization of the vertical magnet 305 which controls the row of contacts 301 at the connector switch 300 in which appears the idle trunk 220. This circuit may be traced from battery, through the winding of magnet 305, thence through the contact of relay 503, outer right front contact of relay 419, to ground at the front contact of relay 402.

Relay 419 also closes operating circuits for the horizontal'magnet 229 of the incoming switch 201 and the horizontal magnet 318 of the connector switch 300. The circuit for magnet 229 may be traced from battery, through the right Winding of said magnet, conductor 230, through the frame connector 500, conductor 514, inner left contact of re-' lay 419, to ground at the contact of relay 402. Magnet 229 rotates the horizontal bar not shown) and extends the trunk 106 over the link 233 to the selected idle trunk'220.

The circuit for magnet 318 may betraced from battery, through the right winding of said magnet, conductor 319, through the connector 502, conductor 514, thence to ground as previously traced. The magnet 318 rotates the horizontal bar (not shown) and completes the connection from the trunk 220 over the link 313 to the called subscribers line 307.

It is understood that the called subscribers line 307 has been previously tested and ascertained to be idle before the connection is extended thereto in the manner described. The manner in which this test is made and also the manner in which the various detailed operations, hereinbefore referred to but not fully shown, take place, may be found in the application to S. B. l Villiams, Serial No. 707,795, filed April 21, 1924. 7

Before proceeding farther with a description of the manner in which the incoming and final switches are held it may be well to explain the difierent conditions under which release of these switches is made necessary. Certain of the operators who supervise connections extending through the incoming and final switches have a no test key 119 associated with their keyboards. The purpose of this key is to'enable the operator to extend a connection to a subscribers line although such line may actually be engaged at the time. By this expedient the operator may go in on a busy connection and infori the called party that a call is waiting his attention. In case of a toll or ot ier impor-. tant long distance call, the called subscriber may desire to discontinue his present conversation and attend to the second call. On the other hand, the called subscriber may wish to disregard the second call, in which case it is necessary for the operator to retire from the connection, releasing the incoming and final switches which she has employed in establishing such second connection. In order to release the connection, the operator restores her release. key 113, which was advanced toits operated position automatically when her assignment key 112 was operated. The restoration of they release key 113 re moves ground from the sleeve conductor for the purpose of releasing the incoming and final switches. However, since the connection has been extended to a busy line, the tendency of this busy condition is to prevent the release of the incoming and final switches of the second connection. The tying-up of these two switches'deprives the operator ofv their use for an appreciable interval of time, producing a marked inefliciency in the employment of the exchange apparatus.

- To obviate this undesirable result, the circuits herein are so arranged that the opera tor may establish a second connection to busy line and may thereafter immediately release the connection, restoring the switches employed notwithstanding the fact'that the line to which such connection was extended presents a busy condition.

The no test key 119 associated with the operators keyboard 105 when operated results in the energization of a no test relay 403located in the marker in the manner described in the application of E. S. Gibson, Serial No. 656,742, filed August 10, 1923, Patent No. 1,559,244, granted October 27, 1925.

It is assumed that the connection which has been previously discussed is one for which the operator did not manipulate her no test key 119. Consequently, the no test relay 403 remains inert and a circuit is established for the relay 210 individual to the operators trunk 220 which was taken for use in extending the connection. This circuit'may be traced from battery, through the winding of relay 210, contact of relay' 503, middle right front contact of relay 419, contact of relay 403, to ground at the contact of relay 402.. Relay 210 operates and closes a temporary locking circuit for itself from battery, through its winding and right contacts, conductor 321, contacts of switch 300, to conductor 512. Since the incoming switch 201 is operated at this time, the relay 114 at the operators position is energized in a circuit from battery, through its winding, sleeve conductor 120, through contacts of switch 201, conductor 238, connector 500, conductor 518, through a contact of relay 4:07, outer left contact of relay 419 to ground. The relay 407 is operated at this time as disclosed in the application of S. B. Williams, Serial No. 707,795, filed April 21, 1924.

Relay 11 1 operates and looks through the release key 113. Relay 114 also applies ground potential to the conductor 120.

Relay 208 is now operated in a circuit from battery, through its normal contact and right winding, over the holding conductor of trunk 220, through the switch 201, to the grounded conductor 120 of trunk 106. Relay 20S operates and locks in a circuit from battery, through the winding of relay 209, outer left front contact of relay 210, inner right contact and right winding of relay 208, to ground as above traced. Slowrelease relay 209 operates in this circuit. The holding circuit for relay 210 is now completed from battery, through its winding and inner right contact, to ground at the outer right contact of relay 209.

As soon as the marker is released and the vertical operating magnets 206 and 20; are deenergized, the connection through switch 201 is maintained by the magnet 229 which is held in a circuit from battery, through both its windings, contacts of switch 201, to the grounded sleeve conductor 120. Similarly, the connector switch 300 is maintained operated by the continued energization of magnet 318 in a circuit from battery, through both its windings, contact .of switch 300, conductor 321, outer right front contact of relay 210, to ground at the outer right contact of relay 209.

The relay 209 completes a circuit for applying ground potential to the sleeve conductor of the called subscribers line 307 to render the same busy, and this circuit may be traced from ground, through the outer right contact of relay 209, conductor 232, through contacts of the switch 300, to the sleeve conductor of the subscribers line 307.

Then it is desired to release the connection, the operator restores her release key 113, thereby removing ground potential from the holding conductor 120. This results in the deenergization of relay 209 and the consequent release of the incoming switch 201. Moreover, the circuit of relays 208 and 209 is opened, resulting in the deenergization of relay 208. Relay 209, how ever, being slow requires an interval in which to retract its arinatures. If the called subscriber 307 has replaced his receiver on the switchhoolr, the relay 209 releases after a measured interval, and in so doing removes ground from the conductor 232, causing the release of relay 210 and of the magnet 318, thereby disconnecting the trunk 220 from the called subscri'bers line and restoring the connector switch 300.

However, if the called subscriber maintains his receiver off the switchhoolr after the operator has released, the relay 209 finds a new energizing circuit, which may be traced as follows: Battery, through the winding and inner right contact of relay 209, right back contact of relay 208, thence over the ring side of the connection, including the loop of the called line 307, and returning over the tip side of the connection through the inner left contact of relay 209, to ground at the inner left back contact of relay 208. Relay 209 therefore remains energized and maintains the busy condition on the holding conductor of trunk 220, pre venting the release of the connector switch 300.

Immediately that relay 208 releases, a circuit is closed from battery, through the winding and contact of the pick-up relay 211, outer left contact of relay 209, outer left contact of relay 208, to the lower contact of interrupter 212. As soon thereafter as the interrupter 212 closes its contact, relay 211 operates and locks to the grounded conductor Upon the next closure of the upper contact of the interrupter 212, a circuit is closed from battery, through the left winding of relay 208, left contact of relay 211, to ground at the contact of interrupter 212. Relay 208 operatesand opens the circuit of relay 209, which releases and causes the release of the connector switch Thus, if the operator fails to manipulate her no test key and the called subscriber maintains his receiver off the switchl1oolr,the connector switch 300 remains in its operated condition until the interrupter 212 measures 0H this predetermined interval of time. By holding the connector switch in its operated condition after the calling subscriber has replaced his receiver, a ground potential is maintained on the sleeve of the called line. This prevents the called line from falsely initiating the operation of a line switch due to the fact that the called subscribers receiver is still off the switchhoolr.

It will next be assumed that the operator is handling a toll or other important connection which she desires to extend to the called subscribers line regardless of whether his line may be busy or not. Accordingly, to anticipate the busy condition of the called line, she manipulates her no test key 119, whereby the no test relay 403 in, the marker is subsequently operated. When the connection is later set up through the incoming and final switches, the relay 219 fails to operate as previously described, since the circuit for energizing the same is now opened at the contact of relay 103.

When the switch 201 operates, relay 208 becomes energized in a circuit traceable from battery, through the contact and right wind ing of said relay, contacts of the switch'201,

to the grounded conductor 120. Relay 208 operates and locks in a circuit from battery, through the left back contact of relay 210, inner right contact and right winding of relay 208, and thence to ground over the sleeve conductor 120 of trunk 105. Since the relay 210 remains deenergized, relay 209 is not furnished with an operating cirwit The connector switch 300 is now held by means of a circuit from battery, through the windings of the horizontal magnet 318, contacts of the switch 316, conductor 321, left inner back contact of relay 210, to ground at the inner left front contact of relay 208. The relay 208 also applies groundpotential to the sleeve conductor of the called subsoribers line 307, in order to render the same busy in case such line is idle. The circuit for this purpose may be traced from ground, through the outer right contact of relay 208, outer right back con,- tact of relay 210, conductor 232, contacts ot the switch 300, to the sleeve conductor of the line 30?. it will be noted in this case that the relay 209 is not connected across the tip and ring conductors of the called subscriber s line. Therefore, it does not matter whether the called line 307 is busy or not. The operator may release the connection which she has extended thereto immediately without waiting for the time measuring device 212.

lVhen the operator desires to release, she throws the release key 113, removing ground pote tial from the conductor 120. This suits the release of switch 201 and also in the release of the relay 208. Relay 208 removes ground potential from conductor 321, whereby the connector switch 300 is re leased immediately.

Consideration will next be given to the establishment of a local connection through one the 'egular incoming selector switches 200. If the subscriber of the line 100 initiates a call, his line is extended through line switch 101 to an idle trunk 102 leading to the district selector switch 103. The trunk 102 is also associated with an idle sender 107 through the sender selector switch 104. After a marker has been associated with the sender, the district selector switch 108 is operated and the connection is extended over an idle trunk 1 15 appearing in the vertical row contacts 213 in the incoming selector switch The f and trunk connectors 500 and 501 and the connecting device are operated for associating the marker ith the proper incoming and final switches w ..n"l also with the proper group of trunlrs interconnecting the same.

It may be assumed that the trunks apearing in the vertical row 216 constitute the switches 300 havin access to the called line Gnly two or these trunks have been con leading to the group of connector shown, but it will be understood that as many will be provided as are necessary.

The marker performs a test of the horizontal lin s in the switch 200 and of the trunks 219, etc., and also of the horizontal linlrs in the connector switch 300, in substanti .lly the same manner as tl at previously discussed in connection with the operation of the switch. 201. In this instance, however, the test circuits for the trunks 21 220, etc, extend through contacts of the trunk connector 501. None of the relays 503 or is operated, due to the fact that the relay 1-04- in the marker remains deenergized. Relay 40 i is not operated owing to the fact that the operators relay 109 in the sender has n t been operated on this type of call. If tie test reveals that the link 235, trunk 220 and link 3123 are idle simultaneously, relay 115) is operated in a circuit from ground over conductor e27, through the back contact of relay 404:, left front contacts of relays 4:08, and 421.0, left baclz contact of relay -11, winding of relay 1 19, to battery. Relay 10 operates and in the manner hereinbefore crihed causes the operation of the hori zontal In .zets and 818 to extend the connection throu-h the switches 200 and 300 to the called subscribers line 307.

In this c" e, the relay 4103 being deenertile relay 210 operates, causing the oaeration. of relay 209 and thereby placing the release of the connector switchBOO and the trunk 220 under the control of the called subscribers line and also under the control of the time measuring device 212.

The release of the connection takes place in substantially the same manner as previously explained herein.

A system of the character hereinbefore described may also be employed for verifying numbers of calling subscribers lines.

Certain other features disclosed in this application are being claimed in a oopending application of S. B. lVilliams, Serial No. 726,268, filed July 16, 1924.

hat is claimed is:

1. In a telephone system, a line, a selective switch, an operators position, means under the control of the operator for extending a connection to said switch, means for operating the switch to further extend the connection to said line, release means at the operators position for releasing the connection to said switch, means controlled by the line for holding said switch operated after the operator has released said connection, and means for placing the release of said switch directly under the control of said release means independently of said line.

2. In a telephone system, a line, a selective switch, an operators position, means under the control of the operator for extending a connection to said switch, means for operating the switch to further extend the connection to said line, release means at the operators position for releasing the connection to said switch, means efi'ective if the line remains busy for holding said switch after the operator has released the connection thereto, and means for enabling said release means to cause the release of said switch simultaneously with the release of the connection regardless of the condition of the line.

3. In a telephone system, a telephone line, an automatic switch, an operators position, means under the control of the operator for extending connection to said automatic switch, means under the control of the operator for operating said switch to further extend the connection to said line, a release key at the operators position for releasing the connection to said switch, means eiiecti've if the line remains busy for holding said switch alter the operator has released the connection thereto, means for releasing said switch at the end of a deth'iite interval after the connection has been released independent of said line, and means for placing tne release of said switch directly under the control of said hey independently of said line.

4. In. a telephone system, a subscribers line, a trunk, means for extending a connection to said trunk, automatic means for ex tending said trunk to the subscribers line,

- release means for releasing the connection to said trunk, means dependent on the continued busy condition 01 said line for holding said trunk in connection therewlth tolsaid switch to further extend the connection to said line, release means at the operators position l'or releasing the connection to said switch, means controlled by the line for.

holding said switch operated after the operator has released said connection, and means rendered effective by said mechanism for placing the release of said switch directly under the control of said release means.

6. In a telephone system, a line, means for extending a connection in the direction oi said line, a selective switch having a number of links for further extending said con nection to said line, means for operating said switch, release means for releasing the con nection extended to said switch, means controlled by the line for holding said switch operated after the operator has released said connection, and means for placing the release of said switch directly under the control of said release means independently of the line.

In witness whereof, I hereunto subscribe my name this lath day of July A. D., 192

EARL S. GIBSON. 

